Hydraulic pump or motor

ABSTRACT

A hydraulic pump or motor includes a cylinder barrel having a plurality of radially extending outwardly open cylinders, a plurality of pistons mounted in the cylinders and projecting therefrom and a gear roller eccentrically mounted on the projecting end of each piston to roll on the inside of a housing on an internal gear and a smooth ring. The ring and rollers carry the main stress load of the pistons while the gearing prevents the rollers from slipping.

United States Patent 1191 Nelson [4 Dec. 9, 1975 [5 HYDRAULIC PUMP 0R MOTOR 2,4l6,940 3/1941 Morton 91/492 27 2 4 121955 H h ..9|492 [75] Inventor: Nels, Cedar Falls 9656:1135 411972 K113113211; 911197 Iowa 3,827,338 8/1974 Oguni et a1, .1 91/491 [73] Assignee: Deere & Company, Moline, 111.

. Primary ExaminerWilliam L. Freeh [22] filed July 1972 Assistant ExaminerG. P1 LaPointe [21] Appl. No; 269,444

[57] ABSTRACT [52] P 91/491; 91/492; 91/183 A hydraulic pump or motor includes a cylinder barrel [51] 'f FOIB 13/06 having a plurality of radially extending outwardly open [58] Fleld of Search 91/478-483, w

91 493 49 V cyllnders, a plurallty of plstons mounted 1n the cyhn [23/44 44 ders and projecting therefrom and a gear roller eccen- 44 B trically mounted on the projecting end of each piston to roll on the inside of a housing on an internal gear [56] References and and a smooth ring The ring and rollers carry the main UNITED STATES PATENTS stress load of the pistons while the gearing prevents 668,855 2/1901 Koetter a. 91/186 h roller from slipping. 800,224 9/1905 Leonard 91/480 905,861 12/1908 Everts et a1 5 91/496 10 Clalmsr 2 Drawmg Flgures US. Patent Dec. 9 1975 HYDRAULIC PUMP OR MOTOR BACKGROUND OF THE INVENTION The present invention relates generally to hydraulic pumps and motors, and more specifically relates to radial piston pumps and motors of the type in which each piston is driven through a plurality of reciprocal cycles for each complete relative revolution between the housing and cyclinder barrel.

Radial piston pumps and motors are well known in the art and are generally of three types. One type of radial piston pump and motor has a cylinder barrel mounted eccentrically to a thrust ring which contacts pistons projecting from the cylinder barrel so that upon relative rotation between the thrust ring and cylinder barrel, the pistons are driven through one reciprocal cycle for each 360 of relative movement between the thrust ring and cylinder barrel. The most notable limitation of this type of radial piston pump or motor is that each piston is limited to a single reciprocal cycle for each complete revolution between the cylinder barrel and thrust ring.

A second type of well known radial piston pump or motor includes an out of round thrust ring coaxial with a cylinder barrel so that the thrust ring would drive each piston through two complete reciprocal cycles for each complete relative revolution between the cylinder barrel and thrust ring. Although this type of radial piston pump or motor has twice the capacity of the first type, its capacity was still unduly limited for some applications.

A third type of radial piston pump or motor includes a generally circular thrust ring mounted coaxial with a cylinder barrel and having a plurality of cam lobes which engage the projecting ends of the pistons and drive the pistons through a plurality of reciprocal cycles for each complete relative revolution between the thrust ring and cylinder barrel. In this type of radial piston pump and motor, the capacity is only limited by the number of cam lobes. However, in this type of pump or motor, it is customary to mount rollers on the ends of the pistons to contact the thrust ring, and the concave and convex surfaces on the ring and roller when the roller is at the peak of one of the cam lobes provides an area of extremely high stress. Also, the extra weight of the rollers which were reciprocated with the pistons increased vibration in the pump or motor.

SUMMARY OF THE INVENTION The principal object of the present invention is to provide an improved radial piston pump or motor.

A more specific object of the present invention is to provide a radial piston pump or motor of the type in which each piston is driven through a plurality of reciprocal strokes for each full revolution and in which the weight of the reciprocating parts is kept at a minimum.

Another object of the present invention is to provide a hydraulic pump or motor of the type in which each piston is driven through a plurality of reciprocal cycles for each full revolution and in which a roller is eccentrically mounted on the projecting end of each piston and moves along a thrust track as the cylinder barrel rotates with respect to the housing.

Still another and more specific object of the present invention is to provide a radial piston pump or motor characterized in that each piston has a gear roller eccentrically mounted on its projecting end which rolls on the inside of the housing on an internal gear and smooth ring so that the ring and rollers carry the main thrust load of the piston while the gearing prevents the rollers from slipping.

The above objects and additional objects and advantages of the present invention will become apparent to those skilled in the art from a reading of the following detailed description taken in conjunction with the accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING In the drawing:

FIG. 1 is a longitudinal cross section of a radial piston pump or motor constructed in accordance with the principles of the present invention; and,

FIG. 2 is a sectional view taken substantially along the line 2-2 of FIG. 1.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing, a pump constructed in accordance with the principles of the present invention is indicated generally at 10 and includes a housing formed with opposite end plates 12 and 14 and a generally circular side wall made of a plurality of alternately stacked internal ring gears 16 and thrust rings 18 which are clamped between the end plates 12 and 14. The end plates, ring gears and thrust rings are all provided with aligned apertures, and bolts 20 extending through the apertures clamp the end plates 12 and 14, ring gears 16 and thrust rings 18 in fluid-tight engagement.

A shaft 22 is journaled in the housing by bearings 24 and 26 which are carried by the end plates 12 and 14 respectively. The shaft 22 extends through the plate 14 and is provided with a flange 28 on its projecting end which serves as a point of connection for some element external of the pump or motor.

A cylinder barrel 30 is mounted on and keyed to the shaft 22 within the housing and is provided with a plurality of arcuately spaced rows of generally radially extending and outwardly open cylinders 32. In the illustrated pump or motor, each row of cylinders includes two axially aligned cylinders which are interconnected by an axially extending bore 34 which communicates with one end of the cylinder barrel. A valve plate 36 is mounted in the housing in a stationary position with respect to the housing and engages the end of the cylinder barrel with which the bores 34 communicate so as to alternately connect each of the cylinders 32 with ports 38 and 40 provided in the end plate 12. The valving function provided by the valve plate 36 and ports 38 and 40 forms no part of the invention but is only intended to be representative of any of the well known valving arrangements used with radial piston pumps and motors.

A piston 42 is reciprocally mounted in each of the cylinders 32 and projects therefrom. Each piston 42 carries a shaft 44 which extends parallel to the axis of the shaft 22, and a pair of gear rollers 46 are eccentrically mounted on each of the shafts 44 on opposite sides of the respective piston 46 so that rotation of the gear rollers drives the pistons through reciprocal cycles. Each of the shafts 44 extends through an aperture provided in the projecting end of its associated piston and is retained in position therein by a locking pin 48.

Each of the gear rollers 46 includes a smooth portion 50 and an outer gear or toothed portion 52. The ring gears 16 and thrust rings 18 provide tracks for the gear rollers with the smooth portions of each pair of gear rollers engaging a common thrust ring and the gear portions of adjacent gear rollers on axially adjacent pistons engaging a common ring gear 16. The meshing teeth of the ring gears 16 and gear rollers 46 cause rotation of the gear rollers upon relative rotation between the shaft 22 and the housing so as to drive the pistons through their reciprocal cycles, and the smooth portions of the gear rollers 46 and the thrust rings 18 carry the main load of the pistons,

The operation of the above-described axial piston pump or motor should be apparent to those skilled in the art, and is essentially as follows. If the apparatus is to be used as a pump. the flange 28 is coupled to some drive means which rotates the shaft 22. Rotation of the shaft 22 causes rotation of the cylinder barrel 30 which in turn causes the gear rollers 46 to roll along their tracks formed by the ring gears 16 and thrust rings 18. Because of the eccentric mounting of the gear rollers 46, their rotation causes the pistons 42 to reciprocate within the cylinders 32. Also, as the cylinder barrel 30 rotates, the valve plate 36 will alternately connect each of the axial bores 34 with the ports 38 and which serve as inlet and outlet ports for a suitable fluid. Thus, I

as each of the pistons 42 moves outwardly, their respective cylinders 32 are connected via the axial bores 34 and valve plate 36 with the inlet port 38 so that fluid under a low pressure flows into the cylinders 32. As the pistons 42 move inwardly, their respective cylinders 32 are connected via the axial bores 34 and valve plate 36 with the outlet port 40 so that fluid under pressure can be forced from the cylinders 32 into the outlet port 40.

If the device is to operate as a motor, fluid under pressure is supplied to one of the ports so as to force the pistons 42 outwardly, The outward movement of the pistons 42 causes rotation of the gear rollers 46 which will cause the shaft 22 to rotate. When the pistons 42 move inwardly, they are connected to the other of the ports so that fluid under low pressure can be exhausted from the cylinders 32.

When the device operates as a pump, it requires a relatively high input torque to the shaft 22 because of the multiple reciprocal cycles of each piston for each revolution of the shaft 22 with respect to the housing, but the volume output of the pump is also relatively high. When the device operates as a motor, it will have a high torque output because of the multiple reciprocal cycles, but the speed of rotation of the shaft 22 will be relatively small, Because of the high torque, low speed output when operating as a motor, hydraulic motors such as that described above have been found to be particularly suitable for use as wheel motors on selfpropelled vehicles.

In addition to providing the multiple reciprocal cycle of each piston for each revolution of the shaft 22 with respect to the housing, the above-described pump or motor has additional advantages. The total weight of the reciprocating parts is kept at a minimum so as to reduce vibration in the assembly. Specifically, because the gear rollers 46 merely roll along either side of the housing, only the pistons reciprocate. Also, both the thrust rings and smooth portions 50 of the gear rollers have concave surfaces which contact each other to carry the thrust load, thus lowering the stress as compared to the stress caused by the concave-convex surface contact common on radial piston cam lobe pumps and motors.

Having thus illustrated and described one preferredv embodiment of the invention and listed its advantages, various modifications within the spirit and scope of the invention will become apparent to those skilled in the art and can be made without departing from the underlying principles of the invention, Therefore, the inven tion should not be limited by the specific illustration and description, but only by the following claims.

I claim:

1. A hydraulic pump or motor comprising: a housing forming a chamber; a shaft mounted in the housing for rotation relative thereto and projecting from one end thereof; a cylindrical barrel in the chamber mounted on and keyed to the shaft and having a plurality of cylin ders open to the chamber with pistons reciprocally mounted therein and projecting flierefrom into the chamber; valving means in the chamber in a fixed position with respect to the housing and operatively associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; a roller joumalled on the projecting end of each piston for rotation about an axis offset from its central axis; each roller having side-by-side smooth and toothed portions; and track means in the housing in engagement with the rollers and including side-by-side smooth and toothed portions cooperating with the smooth and toothed portions of the rollers; whereby, upon relative rotation between the shaft and housing the smooth portions of the rollers and track means carry the main thrust load of the pistons and the toothed portions of the rollers and track means prevent the rollers from slipping.

2. A hydraulic pump or motor as set forth in claim 1 wherein the track means is formed as an integral portion of an internal wall of the housing.

3. A radial piston hydraulic pump or motor comprising: a housing having an internal track means formed on an inner wall thereof; a shaft journaled in the housing coaxial with the track means and projecting from one end of the housing; a cylinder barrel mounted on and keyed to the shaft and having a plurality of generally radially extending and outwardly open cylinders with pistons reciprocally mounted therein and projecting from the open ends thereof; valving means in the housing operatively associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; and roller means journaled on the projecting end of each piston for rotation about an axis eccentric to its central axis; each of the roller means drivingly engaging the track means; whereby upon relative rotation between the shaft and housing, the roller means will move along the track means and cause the pistons to reciprocate or, upon supplying a fluid under pressure to one of the ports in the housing, the reciprocation of the pistons will cause rotation of the roller means which in turn causes relative rotation between the shaft and housing.

4. A radial piston pump or motor comprising: a housing, an internal ring gear and a smooth internal thrust ring therein in side-by-side relationship; a shaft jour naled in the housing coaxial with the ring gear and thrust ring and projecting from one end of the housing; a cylinder barrel mounted on and keyed to the shaft and having a plurality of generally radially extending and outwardly open cylinders with pistons reciprocally mounted therein and projecting from the open ends thereof; valving means in the housing associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; and a gear roller eccentrieally iournaled on the projecting end of each piston; each gear roller in cluding a smooth portion in engagement with the thrust ring and a gear portion meshing with the ring gear 5. A radial piston pump or motor as set forth in claim 4 wherein the ring gear and thrust ring are formed as an integral part of the interior wall of the housing.

6. A radial piston pump or motor as set forth in claim 5 wherein there are a plurality of ring gears and thrust rings formed on the interior wall of the housing, and the cylinder barrel has a plurality of arcuately spaced rows of axially aligned cylinders.

7. A radial piston pump or motor as set forth in claim 6 wherein a generally circular side wall of the housing is formed from a plurality of individual ring gears and thrust rings alternately stacked together and clamped between opposite housing end plates.

8. A radial piston pump or motor as set forth in claim 7 wherein a pair of gear rollers are mounted on the pro jecting end oleach piston \lllll one gear roller on each side thereofi 9. A radial piston pump or motor as set forth in claim 8 wherein the smooth portion of each gear roller is ad jacent its associated pistorr the smooth portions of the pair of gear rollers for each piston engage a common thrust ring and the adjacent gear portions of the gear rollers on each pair of axially adjacent pistons mesh with a common ring gear.

ID. A radial piston pump or motor as set forth in claim 5 wherein a pair of gear rollers are mounted on opposite sides of the projecting end of each piston with the smooth portions ofthe gear rollers adjacent the piston, and the smooth portions of the pair of gear rollers on each piston engage a common thrust ring.

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1. A hydraulic pump or motor comprising: a housing forming a chamber; a shaft mounted in the housing for rotation relative thereto and projecting from one end thereof; a cylindrical barrel in the chamber mounted on and keyed to the shaft and having a plurality of cylinders open to tHe chamber with pistons reciprocally mounted therein and projecting therefrom into the chamber; valving means in the chamber in a fixed position with respect to the housing and operatively associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; a roller journalled on the projecting end of each piston for rotation about an axis offset from its central axis; each roller having side-by-side smooth and toothed portions; and track means in the housing in engagement with the rollers and including side-by-side smooth and toothed portions cooperating with the smooth and toothed portions of the rollers; whereby, upon relative rotation between the shaft and housing the smooth portions of the rollers and track means carry the main thrust load of the pistons and the toothed portions of the rollers and track means prevent the rollers from slipping.
 2. A hydraulic pump or motor as set forth in claim 1 wherein the track means is formed as an integral portion of an internal wall of the housing.
 3. A radial piston hydraulic pump or motor comprising: a housing having an internal track means formed on an inner wall thereof; a shaft journaled in the housing coaxial with the track means and projecting from one end of the housing; a cylinder barrel mounted on and keyed to the shaft and having a plurality of generally radially extending and outwardly open cylinders with pistons reciprocally mounted therein and projecting from the open ends thereof; valving means in the housing operatively associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; and roller means journaled on the projecting end of each piston for rotation about an axis eccentric to its central axis; each of the roller means drivingly engaging the track means; whereby upon relative rotation between the shaft and housing, the roller means will move along the track means and cause the pistons to reciprocate or, upon supplying a fluid under pressure to one of the ports in the housing, the reciprocation of the pistons will cause rotation of the roller means which in turn causes relative rotation between the shaft and housing.
 4. A radial piston pump or motor comprising: a housing, an internal ring gear and a smooth internal thrust ring therein in side-by-side relationship; a shaft journaled in the housing coaxial with the ring gear and thrust ring and projecting from one end of the housing; a cylinder barrel mounted on and keyed to the shaft and having a plurality of generally radially extending and outwardly open cylinders with pistons reciprocally mounted therein and projecting from the open ends thereof; valving means in the housing associated with the cylinder barrel to alternately interconnect each of the cylinders with first and second ports provided in the housing; and a gear roller eccentrically journaled on the projecting end of each piston; each gear roller including a smooth portion in engagement with the thrust ring and a gear portion meshing with the ring gear.
 5. A radial piston pump or motor as set forth in claim 4 wherein the ring gear and thrust ring are formed as an integral part of the interior wall of the housing.
 6. A radial piston pump or motor as set forth in claim 5 wherein there are a plurality of ring gears and thrust rings formed on the interior wall of the housing, and the cylinder barrel has a plurality of arcuately spaced rows of axially aligned cylinders.
 7. A radial piston pump or motor as set forth in claim 6 wherein a generally circular side wall of the housing is formed from a plurality of individual ring gears and thrust rings alternately stacked together and clamped between opposite housing end plates.
 8. A radial piston pump or motor as set forth in claim 7 wherein a pair of gear rollers are mounted on the projecting end of each piston with one gear roller on each side thereof.
 9. A radial piston pump or motor as set forth in claim 8 wherein the smooth portion of each gear roller is adjacent its associated piston, the smooth portions of the pair of gear rollers for each piston engage a common thrust ring, and the adjacent gear portions of the gear rollers on each pair of axially adjacent pistons mesh with a common ring gear.
 10. A radial piston pump or motor as set forth in claim 5 wherein a pair of gear rollers are mounted on opposite sides of the projecting end of each piston with the smooth portions of the gear rollers adjacent the piston, and the smooth portions of the pair of gear rollers on each piston engage a common thrust ring. 